﻿/*
Microsoft Limited Permissive License (Ms-LPL)

This license governs use of the accompanying software. If you use the software, you accept this license. If you do not accept the license, do not use the software.

1. Definitions

The terms “reproduce,” “reproduction,” “derivative works,” and “distribution” have the same meaning here as under U.S. copyright law.
A “contribution” is the original software, or any additions or changes to the software.
A “contributor” is any person that distributes its contribution under this license.
“Licensed patents” are a contributor’s patent claims that read directly on its contribution.

2. Grant of Rights

(A) Copyright Grant- Subject to the terms of this license, including the license conditions and limitations in section 3, each contributor grants you a non-exclusive, worldwide, royalty-free copyright license to reproduce its contribution, prepare derivative works of its contribution, and distribute its contribution or any derivative works that you create.
(B) Patent Grant- Subject to the terms of this license, including the license conditions and limitations in section 3, each contributor grants you a non-exclusive, worldwide, royalty-free license under its licensed patents to make, have made, use, sell, offer for sale, import, and/or otherwise dispose of its contribution in the software or derivative works of the contribution in the software.

3. Conditions and Limitations

(A) No Trademark License- This license does not grant you rights to use any contributors’ name, logo, or trademarks.
(B) If you bring a patent claim against any contributor over patents that you claim are infringed by the software, your patent license from such contributor to the software ends automatically.
(C) If you distribute any portion of the software, you must retain all copyright, patent, trademark, and attribution notices that are present in the software.
(D) If you distribute any portion of the software in source code form, you may do so only under this license by including a complete copy of this license with your distribution. If you distribute any portion of the software in compiled or object code form, you may only do so under a license that complies with this license.
(E) The software is licensed “as-is.” You bear the risk of using it. The contributors give no express warranties, guarantees or conditions. You may have additional consumer rights under your local laws which this license cannot change. To the extent permitted under your local laws, the contributors exclude the implied warranties of merchantability, fitness for a particular purpose and non-infringement.
(F) Platform Limitation- The licenses granted in sections 2(A) & 2(B) extend only to the software or derivative works that you create that run on a Microsoft Windows operating system product.
 */

using System;
using System.Collections.Generic;
using System.Text;
using System.Xml;
using System.Configuration;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using System.Security.Cryptography.Xml;
using System.Collections.Specialized;


namespace Pkcs12ProtectedConfigurationProvider
{
    public class FastEncryptionWorkaround
    {
        public string Thumbprint;
        public string Encrypt(string iSource)
        {
            var aCryptoProvider = this.GetCryptoServiceProvider(true);
            byte[] aInputBytes = Encoding.UTF8.GetBytes(iSource);
            var aEncryptedBlock = aCryptoProvider.Encrypt(aInputBytes, false);
            return Convert.ToBase64String(aEncryptedBlock);
        }

        public string Decrypt(string iSource)
        {
            var aCryptoProvider = this.GetCryptoServiceProvider(false);
            byte[] aInputBytes = Convert.FromBase64String(iSource); //Encoding.UTF8.GetBytes(input);
            var aDecryptedBlock = aCryptoProvider.Decrypt(aInputBytes, false);
            return Encoding.UTF8.GetString(aDecryptedBlock);
        }

        private byte[] GetRandomKey()
        {
            byte[] data = new byte[0x18];
            new RNGCryptoServiceProvider().GetBytes(data);
            return data;
        }

        /// <summary>
        /// Get either the public key for encrypting configuration sections or the private key to decrypt them. 
        /// </summary>
        /// <param name="iIsEncryption"></param>
        /// <returns></returns>
        private RSACryptoServiceProvider GetCryptoServiceProvider(bool iIsEncryption)
        {
            RSACryptoServiceProvider aCryptoProvider;
            var aCertificate = GetCertificate(Thumbprint);
            if (iIsEncryption)
            {
                aCryptoProvider = (RSACryptoServiceProvider)aCertificate.PublicKey.Key;
            }
            else
            {
                aCryptoProvider = (RSACryptoServiceProvider)aCertificate.PrivateKey;
            }
            return aCryptoProvider;
        }

        /// <summary>
        /// Get certificate from the Local Machine store, based on the given thumbprint
        /// </summary>
        /// <param name="iThumbprint"></param>
        /// <returns></returns>
        private X509Certificate2 GetCertificate(string iThumbprint)
        {
            var aCertStore = new X509Store(StoreName.My, StoreLocation.LocalMachine);
            aCertStore.Open(OpenFlags.ReadOnly);
            var aCertFound = aCertStore.Certificates.Find(X509FindType.FindByThumbprint, iThumbprint, false);
            //specify false here, since self-signed certificates are not considered to be valid valid
            aCertStore.Close();
            if (aCertFound.Count == 0)
            {
                throw new ApplicationException(string.Format("No certificate was found for thumbprint {0}", iThumbprint));
            }

            return new X509Certificate2(aCertFound[0]);
        }

    }
}
